Common Waste Research Articles

MgO/fluid catalytic cracking (FCC) ash blends for 3D printing on vertical surfaces

Fluid catalytic cracking (FCC) ash is a common industrial waste in the crude oil refinery process. In this study, raw FCC ash was incorporated to develop sustainable MgO/FCC ash blends for 3D printing on vertical surfaces. Rheological and tack behaviors of MgO/FCC ash blends were systematically studied, followed by the assessment of mechanical property and hydration products. On this basis, the suitable mixture for 3D printing on the vertical surfaces was determined, and its feasibility was verified with lab-scale 3D printing. Finally, the environmental impact of the developed mixture was estimated through batch leaching and composition tests. This study provides an alternative method to upcycle FCC ash as an ingredient for 3D concrete printing, which brings benefits to both the construction and oil refinery industries. Besides, the rheological, tack, and hydration investigations of the MgO/FCC ash blends guide the future design of similar mixtures with upcycled wastes.

An Overview of the Utilization of Common Waste as an Alternative Fuel in the Cement Industry

As concrete is one of the most commonly used construction materials, there is a massive production of cement, which causes cement manufacturing to be an energy-intensive industry. A significant amount of the cost of cement production, ranging from 20% to 25%, is attributed to thermal energy. In addition, the action of mining and burning fossil fuels results in the unfavorable emission of hazardous compounds into the environment. Therefore, the switch from conventional fossil fuels to alternative fuels (AFs) in the cement manufacturing business has attracted attention due to environmental and financial concerns. In this paper, four commonly used AFs are discussed, which are waste tires, municipal solid waste, meat and bone meal, and sewage sludge. It is found that each AF has a unique calorific value and properties, attributed to its source, treatment, and technology. Furthermore, the availability of AF is important as the amount varies depending on the location. In addition, their effects on gaseous emissions from the cement plant and the quality of clinker are found to be inconsistent. Thus, there will not be a single best type of AF option to be used in the cement industry. A good AF should be able to provide sufficient thermal energy while reducing the environmental impacts and costs. A careful analysis and multicriteria decision-making approach are always vital when employing AFs in order to prevent environmental problems, cost increases, as well as clinker quality degradation.

New insights for improving low-rank coal flotation performance via emulsified waste fried oil collector

A novel emulsified waste fried oil collector (EWFOC) of the oil-in-water (O/W) type was prepared via transesterification and ultrasonic emulsification, and to be used as an alternative collector to improve the flotation performance of low-rank coal while reducing the collector dosage. The preparation process of EWFOC was optimized, and its performance was compared to that of a common collector (diesel) and waste fried oil collector (WFOC) in the flotation of long-flame coal collected from two top coal-producing province (autonomous region) in China. The micrograph, particle size distribution and dispersion of EWFOC were observed under optical microscope. In addition, the functional groups and wettability were also analyzed. The optimized emulsification conditions for EWFOC were determined as HLB = 14.0, emulsifier dosage of 1 %, oil–water ratio of 3:7, ultrasonic time of 5 min, and a NaCl concentration of 0.02 mol/L. Compared to diesel, WFOC improved the recovery of clean coal and reduced the ash content of clean coal. EWFOC, on the other hand, demonstrated better flotation performance, resulting in up to a 70 % reduction in WFOC dosage. This significant improvement is attributed to the cavitation mechanism of phacoemulsification, which renders EWFOC stable in water with homogenous dispersion and enhances its attachment to coal particles. EWFOC showed better performance compared to diesel and WFOC in terms of improved contact angle as well as adherence to oxygen-containing functional groups (especially O=C–O and C–O) on the surface of long-flame coal, thus enhancing the hydrophobicity of the said coal.

Effect on mechanical properties and microstructure of high-strength eco-friendly concrete with waste glass powder-eggshell particles

Waste glass and discarded eggshells are common solid waste materials. In order to explore a new type of high-strength eco-friendly concrete, waste eggshell particles (ESP) combined with waste glass powder (GP) to replace the same mass of cement was used to prepare waste eggshell particles-waste glass powder concrete (ESGPC) in this study. The compressive strength and splitting strength of the specimens were tested using a universal testing machine. Meanwhile, the NMR technique was applied to test the pore structure of the specimens, the scanning electron microscope was used to investigate the microscopic morphology of the hydration products, and the distribution of GP and ESP in the specimens was investigated by the energy spectrum analyzer. The modification mechanisms of GP and ESP on the workability and mechanical properties of ordinary high-strength concrete were summarized. The results showed that as the content of ESP-GP increased, the slump of fresh concrete gradually increased, the compressive strength and splitting tensile strength first increased and then decreased, and the best replacement rate of ESGPC was 20%; the porosity of concrete initially decreased and then increased, and the number of gel pores (<10 nm) and transition pores (10 nm∼100 nm) increased with the increase of ESP-GP content. When the substitution rate of ESGPC reaches 40%, there is a significant decrease in the number of macropores (>1000 nm) and capillary pores (100 nm∼1000 nm). After analysis by the grey entropy correlation comprehensive analysis method, it was discovered that the volume of transition pores had the strongest correlation with the compressive strength of ESGPC; ESP-GP formed an amorphous film to compensate for the characteristics of weak bond in the transition zone of concrete.

Effects of peptide fractions and amino acids on antioxidant properties of autolyzed tuna viscera protein hydrolysate

Tuna viscera as a common waste product from the tuna processing industry contributes to environmental pollution. The effects were determined of peptide fractions and amino acids on the antioxidant properties of protein hydrolysate from tuna viscera. We converted this waste into protein hydrolysate, a high added-value product, using autolysis. Tuna protein hydrolysate was fractionated by ultrafiltration into four fractions (&gt;10 kDa, 5–10 kDa, 1–5 kDa and &lt;1 kDa) and each was examined for its antioxidant properties (DPPH, ABTS, FRAP and metal chelating) and amino acids composition. The MW and amino acids of the tuna protein hydrolysate peptide fractions were not directly correlated with DPPH radical scavenging activity and metal chelating. The ABTS radical scavenging activity and ferric reducing antioxidant power (FRAP) of the 1–5 kDa fraction were higher than for the other fractions. The tuna protein hydrolysate peptide fractions contributed to antioxidant activity and should be used to their full advantage by the nutritional and food industries

Online source tracing of waste paper by smoke based on laser-induced breakdown spectroscopy

Paper is a widely used material and common recyclable household waste in waste disposal, which gets more attention nowadays for the misclassification of recyclable waste. In this work, an online source tracing system combined with machine learning algorithms to identify and classify the smoke of waste paper incineration based on laser-induced breakdown spectroscopy (LIBS) was established. Four types of waste paper, including tissue, corrugated paper, printing paper, and newspaper, were taken as examples. The smoke of four different waste papers was detected by LIBS and then further analyzed. The detected spectra with C, N, O, Mg, Al, and Ca could hardly be distinguished artificially. The random forest algorithm and the linear discriminant analysis were introduced to classify the smoke, and its accuracy reached 95.83%. The results indicate that source tracing of waste paper can be realized by identifying and classifying the smoke via the developed system. This could provide some reference for helping us to monitor the effectiveness of waste classification and incineration and monitor the atmosphere pollution.

Bokashi fermentation of brewery’s spent grains positively affects larval performance of the black soldier fly Hermetia illucens while reducing gaseous nitrogen losses

Digestion of waste feedstocks by larvae of the black soldier fly Hermetia illucens (Diptera: Stratiomyidae) (BSF) results in proteins for animal feed and organic fertilizer with a reduced environmental footprint, but it can still have negative environmental effects through greenhouse gas (GHG) and ammonia (NH3) emissions. Both biomass conversion by BSF larvae and associated GHG and NH3 emissions can depend on substrate properties that may be optimized through microbial inoculation pre-treatments, such as bokashi fermentation. Here, we quantified the effects of bokashi fermentation of brewery’s spent grains on BSF rearing metrics and associated GHG and NH3 emissions at benchtop scale. We found that bokashi fermentation increased larval biomass by 40% and shortened development time by over two days on average, compared with unfermented spent grains. In line with increased larval growth, CO2 emissions in BSF larvae treatments were 31.0 and 79.0% higher in the bokashi fermented spent grains and Gainesville substrates, respectively, compared to the unfermented spent grains. Adding BSF larvae to the spent grains increased cumulative N2O emissions up to 64.0 mg N2O kg substratedry-1 but there were essentially no N2O emissions when larvae were added to fermented spent grains. Bokashi fermentation also reduced NH3 fluxes from the volatilization of substrate nitrogen in the BSF larvae treatment by 83.7-85.8% during days 7 and 9, possibly by increasing N assimilation by larvae or by reducing the transformation of substrate NH4+ to NH3. Therefore, bokashi fermentation may be applied to improve performance of BSF larvae on a common industrial waste stream and reduce associated emissions.

Innovative Use of Waste PET-Derived Additive to Enhance Application Potentials of Recycled Concrete Aggregates in Asphalt Rubber.

Polyethylene terephthalate (PET) drinking bottles, rubber tires, and concrete are the very common municipal solid wastes, which are usually disposed of at landfills and stockpiles and cause continuous damage to the environment. Some studies have indicated that waste PET can be chemically converted into an additive for improving the overall properties of asphalt pavement incorporating natural aggregates, especially the moisture-induced damage resistance. However, it is not clear whether this PET additive still works for asphalt rubber containing recycled concrete aggregates (RCA). To well reveal this issue, this study first adopted a similar way to chemically recycle waste PET into the additive for modifying crumb rubber modified asphalt (CRMA) binder and then mixed the binder with the 13 mm maximum aggregate stone matrix asphalt containing 100% coarse RCA for preparing the mixtures. After a series of physicochemical characterizations of the PET additive, the moisture resistance, rutting resistance, low-temperature cracking resistance, and fatigue resistance of the mixture were systematically evaluated. The results showed that the PET additive is capable of improving the resistance to moisture and high-temperature deformation of asphalt rubber and helps greatly reduce the moisture-induced damage to the interfacial bonding layer. To be more detailed, the residual Marshall stability (RMS) value of RCA-CRMAM/1PET after 72 h of immersion is higher than 85% by contrast to that of RCA-CRMAM (77.1%), while the tensile strength ratio (TSR) value of RCA-CRMAM/1PET shows more than 80% compared to that of 65.2%. In addition, only 1% PET additive can enhance the high-temperature resistance of asphalt rubber containing RCA to rut and allow it to maintain higher resistance to rut after moisture-induced damage. 1% PET additive can help improve the bearing capacity of RCA-CRMAM under a low-temperature environment and delay its fatigue life at small stresses. Generally, with the successful introduction of PET additives to asphalt rubber containing RCA, more durable and sustainable highway pavement can be produced and applied in practice to alleviate the negative impacts caused by waste PET, waste tire rubber, and waste concrete.

Converting waste to resource: Utilisation of elemental S and consortia of halo–alkaliphilic S–oxidisers for preparation of acidified compost from organic wastes

Utilising the acidulated manures is a reliable option for plant nutrition and managing alkalinity stress. This study characterizes the common wastes and their acidulation potential through consortia of microbes like Priestia aryabhattai, Stutzerimonas stutzeri and Pseudomonas chloritidismutans and elemental sulphur (S°). The poultry manure (PM) and pressmud (Pmud) were rich in N, P, and phenol with a narrow C/N ratio. The water–soluble total N (TNsol), dissolved organic N (DON), NO3−–N was greater in cattle manure. Acidulation of manure declined pH by 0.5–2.5 units and increased titratable acidity (TA) and equivalent alkalinity neutralisation potential (EANP) by 5034.8 and 2,805,732.3 me kg−1, respectively. The incubation for 28 days was optimum for acidulation. The water–soluble SO42−, Mg2+, and DOC were the key variables explaining variability in EANP. The rapid acidulation of manure using microbial consortia and S° could be a pragmatic approach for recycling and reusing the waste.

Chromium removal from chromium gypsum through microwave hydrothermal crystal phase regulation.

Chromium gypsum (CG) is a common hazardous waste formed in chromium salt or electroplating industries. The trapped or lattice-doped CrO42- in gypsum crystals are difficult to be reduced or removed by traditional methods, which will be re-oxidized or slowly released during long-term hypaethral storage. In this study, microwave hydrothermal treatment was applied to remove chromium in CG. Under optimal conditions (solid-liquid ratio of 1:5, 0.1M sulfuric acid as liquid media, and 110°C), over 99% of the chromium in CG can be removed within 10min. XRD spectra indicated that 59.8% gypsum was transformed to from dihydrate gypsum to hemihydrate gypsum. The toxicity leaching test shows that chromium in CG is 377.0mg/L before detoxification and 0.55mg/L after detoxification, which proves that chromium in CG lattice can be efficiently removed. This work enables to significantly advance the dehydration phase transformation process of gypsum and release the heavy metal impurities within it more quickly and provides new possibilities to treat similar solid waste containing gypsum or minerals with hydration water.

Effect of Hydrochar Modification on the Adsorption of Methylene Blue from Aqueous Solution: An Experimental Study Followed by Intelligent Modeling

Wheat straw, which is a carbon-rich precursor and a common agriculture waste in Sanandaj, was modified to produce hydrochar with high adsorption capacity by the hydrothermal carbonization (HTC) method. The hydrochars were tested as adsorbents to remove methylene blue (MB) from aqueous solution, and the effects of various interfering parameters, including pH, MB concentration, and adsorbent dosage, were investigated using artificial neural networks (ANNs) on adsorption modeling. Adsorption isotherms and kinetics were studied to explain the MB adsorption process. The prepared hydrochars were characterized using Brunauer–Emmett–Teller (BET), scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDAX), and high-performance liquid chromatography (HPLC) instruments. The maximum MB removal efficiency achieved by hydrochar modified by KOH (0.1 M) and adsorption data fitted well with the Langmuir isotherm and pseudo-second-order kinetics. In terms of elemental composition, the hydrochar sample contained 52.19% carbon (C), 3.37% hydrogen (H), 0.1% nitrogen (N), 0.15% sulfur (S), and 35.66% oxygen (O). The ash content in the sample was 8.50%. The recorded hydrogen-to-carbon ratio (H/C) and oxygen-to-carbon ratio (O/C) indicated a shift towards humification, implying the influence of KOH addition during the hydrochar production process. Additionally, the specific surface area of the hydrochar, as measured by the BET method, was found to be 11.54 m²/g. Among the aromatics, a significant presence of hydroxymethylfurfural (HMF) was detected, with a concentration of 4.70 g/kg DM. The modeling results demonstrated that the concentration of MB had the most substantial impact on the predicted removal, followed by pH, adsorbent dosage, and contact time.

Investigation of proteinaceous algal biomass as a drilling fluid component

This study represents the first investigation into the potential of Spirulina algae proteins as drilling fluid constituents to address the problems of the environmental impacts of the petroleum industry. Algae protein is a common waste product from many bioprocessing operations including biofuel production, so this work also presents a solution to a waste utilization problem for bioprocessing industries. As such, this technology could create an important coproduct for bioprocessing industries while providing more sustainable and environmentally-benign drilling fluids for the petroleum industry. Algae biomass was hypothesized to serve as a bentonite replacement or as an additive that could improve drilling fluid performance by reducing fluid loss via permeation, and/or improvement of lubricity via reduction in coefficient of friction. Measurements were taken in accordance with API RP 13B-1 using an OFITE viscometer, OFITE 4-Unit HTHP Filter Press, and OFITE extreme pressure and lubricity tester. The rheological tests include viscosity, yield stress, and gel strength. Key findings include a friction reduction of up to 27% and a standard fluid loss as low as 13.5 mL. The biomass was able to increase the viscosity of the drilling fluids and exhibited a shear-thinning rheology with yield points exceeding 40 lbf/ft2. The rheology was fitted to the Bingham plastic model and the Herschel-Bulkley model. These findings have potential impacts in the fields of petroleum, chemical, environmental, and material engineering. It is concluded that Spirulina biomass is a good potential additive for decreasing fluid loss and improving the lubricity of drilling fluids, but it will not suffice as a bentonite replacement.

Evaluation of Storage and Disposal of Household Waste in the City of Kinshasa (Communes of Lemba, Mont-Ngafula, and Kisenso) and Awareness of Eco-Citizenship

This study aims to analyze and describe the characteristics of household waste in the communes of Lemba, Mont-Ngafula and Kisenso in Kinshasa, while raising awareness of ecological citizenship. The study was conducted from April 17 to May 3, 2023, with a sample of 690 households, 138 randomly selected from each community. The main methods used are survey, interview and observation in the field.&#x0D; The results show that household waste management in the cities studied does not contribute to sustainable development. Most households use garbage cans, mainly buckets and bags, but waste sorting is rare, except in the Kindele area. The most common waste disposal methods are inappropriate local disposal and incineration. The most common methods of waste disposal are disposal in inappropriate locations and incineration. Average waste weights vary by neighbourhood, with values ranging from 8.67 kg to 13.99 kg per household. It has a significant correlation between the total weight of waste generated per household and household size.&#x0D; The findings of the study indicate that the state of household waste management in these cities is worrying, with adverse consequences for the environment and public health. Proposals include new laws to regulate waste management, integration of waste management into urban development plans, establishment of landfills and public awareness of sanitation rules and the principles of waste reduction, reuse and recycling. Developing effective and sustainable strategies to address household waste management in these communities in Kinshasa is crucial. The involvement of local authorities, stakeholders and citizens is essential to protect the environment.

Hydrothermal carbonization pretreatment makes a remarkable difference in activation of rice and lettuce in food waste

Cooked rice and the vegetables like lettuce are common kitchen waste, which are carbonaceous materials and have the potential as feedstock for the production of activated carbon. Cooking is similar to hydrothermal treatment (HTC), which might impact the subsequent activation of kitchen waste. In this study, the HTC of lettuce, rice, or their mixture and the activation of the resulting hydrochars were conducted. The results indicated that cross-polymerization between the N-containing organics from lettuce and the sugar derivatives from rice took place in their co-HTC, which significantly increased the hydrochar yield. Activation of the hydrochar from the co-HTC generated the AC with a yield of 2 times that from direct activation of mixed lettuce/rice. However, the co-HTC facilitated aromatization, reducing reactivity with K2C2O4 in activation and producing the AC with main micropores and low specific surface area. Activation of the hydrochar from HTC of rice followed the above trend, while that from lettuce was the opposite. The organics in lettuce were thermally unstable and could not undergo sufficient aromatization. The activation of hydrochar from HTC of lettuce thus generated the AC with the lowest yield, but the highest specific surface area (1684.9 m2/g), abundant mesopores, and superior capability for adsorption of tetracycline. However, the environmental impacts and energy consumption for the production of AC from the hydrochar of lettuce were higher than that from hydrochar of co-HTC.

An assessment of the current situation and recommendation of management scenarios for municipal solid waste management in Ho Chi Minh city

Ho Chi Minh city (HCMC) is currently facing a critical problem of the uncontrollable municipal solid waste (MSW). The most common waste disposal practice in the city is landfilling, but this is not a sustainable solution. From 2010 to 2022, the amount of waste generated has increased annually, from 6,000 tons/day to 9,200 tons/day, with an average growth rate of 6-8% per year. This study calculated the average emission factor of various districts in the city such as districts 1, 3, etc. at 0.83 kg/capita/day and district Binh Chanh, Cu Chi, etc. at 0.73 kg/capita/day and forecasted that the amount of waste will reach approximately 16,100 tons/day by 2050. Currently, 80-90% of collected MSW is landfilled, while only 10% is recycled. Composting and energy recovery practices are rarely used. This paper reviewed the current solid waste practice in HCMC and proposed four management scenarios to develop a sustainable solid waste management system. The first scenario is landfilling, which involves non-segregated waste disposal at the source. The second scenario is recycling, which involves segregating waste at the source for recycling, reuse, and waste reduction. The third scenario is composting, which requires using a mechanical-biological treatment plant for sorting, composting, and producing fuel from waste. The fourth scenario is waste-to-energy, which uses a waste incineration plant to generate energy from waste.

MIL-53(Al) assisted in upcycling plastic bottle waste into nitrogen-doped hierarchical porous carbon for high-performance supercapacitors

Disposable aluminum cans and plastic bottles are common wastes found in modern societies. This article shows that they can be upcycled into functional materials, such as metal-organic frameworks and hierarchical porous carbon nanomaterials for high-value applications. Through a solvothermal method, used poly(ethylene terephthalate) bottles and aluminum cans are converted into MIL-53(Al). Subsequently, the as-prepared MIL-53(Al) can be further carbonized into a nitrogen-doped (4.52 at%) hierarchical porous carbon framework. With an optical amount of urea present during the carbonization process, the carbon nanomaterial of a high specific surface area of 1324 m2 g−1 with well-defined porosity can be achieved. These features allow the nitrogen-doped hierarchical porous carbon to perform impressively as the working electrode of supercapacitors, delivering a high specific capacitance of 355 F g−1 at 0.5 A g−1 in a three-electrode cell and exhibiting a high energy density of 20.1 Wh kg−1 at a power density of 225 W kg−1, while simultaneously maintaining 88.2% capacitance retention over 10,000 cycles in two-electrode system. This work demonstrates the possibility of upcycling wastes to obtain carbon-based high-performance supercapacitors.

Maximizing the electrochemical performance of supercapacitor electrodes from plastic waste

The management of the increasing volume of plastic waste has become a key challenge for society. A promising strategy now consists in the transformation of plastic waste into high-value materials that can be utilized in energy storage devices such as batteries and supercapacitors. In this study, we demonstrate a two-step procedure, involving pyrolysis, followed by chemical activation that will convert common plastic waste into activated carbons (ACs). This technique makes ACs suitable for supercapacitor electrode materials. Further, the electrochemical performance of ACs is outstanding in terms of capacitance, energy density, and cycling stability. Besides the well-established parameters, including a specific surface area and micropore volume, we found that other critical factors such as polymer glass transition temperature, polymer-activating agent miscibility, activating agent (K2CO3):AC ratio, and AC water dispersion stability also play a crucial role in determining the supercapacitors performance. Controlling these parameters, we obtained ACs as supercapacitor electrodes from a range of plastic waste materials with a competitive electrochemical performance. Specifically, the ACs exhibited a specific capacitance of 220 F g−1 (at a current density of 1 A g−1), energy and power densities of 61.1 Wh kg−1 and 36.9 kW kg−1, respectively, and excellent cycling stability (95 % retention after 30,000 cycles). Our findings provide a pathway towards transforming plastic waste into valuable electrode materials for supercapacitors.

The Corrosion Resistance of Reinforced Reactive Powder Concrete with Secondary Aluminum Ash Exposed to NaCl Action.

Secondary aluminum ash (SAA) is a type of common solid waste which leads to pollution without treatment. Due to its chemical reactivity, the application of SAA to reactive powder concrete (RPC) may help solidify this solid waste while increasing its performance. However, RPC is usually in active service when used with steel bars. NaCl can corrode the steel bars when reinforced RPC is used in a coastal environment. In this study, the corrosion resistance of reinforced RPC was investigated. The specimens were exposed to an environment of NaCl with freeze-thaw cycles (F-Cs) and dry-wet alternations (D-As). The corresponding mass loss rates (MRs), the electrochemical impedance spectroscopy (EIS) curves and the dynamic modulus of elasticity (DME) were measured. The results show that the MR and the DME of reinforced RPC decrease with increasing values of F-C and D-A. F-C and D-A increases lead to increased electrical resistance (R). The real part value corresponding to the extreme point of the EIS curve is increased by 0~213.7% when the SAA is added. The relationship between the imaginary part and the real part of the EIS fits the quadratic function. The equivalent circuit of the reinforced RPC is obtained from the EIS curves. The R of the rust is calculated by using the equivalent circuit. The rust's R decreases in the quadratic function with the mass ratio of the SAA. After 200 NaCl F-Cs, the MR, the DME and the R vary within the ranges of 23.4~113.6%, -2.93~-4.76% and 4.92~13.55%. When 20 NaCl D-As are finished, the MR, the DME and the R vary within the ranges of 34.7~202.8%, -13.21~-14.93% and 120.48~486.39%. The corrosion area rates are 2.3~68.7% and 28.7~125.6% higher after exposure to 200 NaCl F-Cs and 20 NaCl D-As. When the SAA is mixed, the MR is decreased by 0~13.12%, the DME increases by 0~3.11%, the R of the reinforced RPC increases by 26.01~152.43% and the corrosion area rates are decreased by 21.39~58.62%. This study will provide a novel method for solidifying SAA while improving the chlorine salt resistance of RPC.

Metabolic engineering of Escherichia coli for 2,4-dinitrotoluene degradation

2,4-Dinitrotoluene (2,4-DNT) as a common industrial waste has been massively discharged into the environment with industrial wastewater. Due to its refractory degradation, high toxicity, and bioaccumulation, 2,4-DNT pollution has become increasingly serious. Compared with the currently available physical and chemical methods, in situ bioremediation is considered as an economical and environmentally friendly approach to remove toxic compounds from contaminated environment. In this study, we relocated a complete degradation pathway of 2,4-DNT into Escherichia coli to degrade 2,4-DNT completely. Eight genes from Burkholderia sp. strain were re-synthesized by PCR-based two-step DNA synthesis method and introduced into E. coli. Degradation experiments revealed that the transformant was able to degrade 2,4-DNT completely in 12 h when the 2,4-DNT concentration reached 3 mM. The organic acids in the tricarboxylic acid cycle were detected to prove the degradation of 2,4-DNT through the artificial degradation pathway. The results proved that 2,4-DNT could be completely degraded by the engineered bacteria. In this study, the complete degradation pathway of 2,4-DNT was constructed in E. coli for the first time using synthetic biology techniques. This research provides theoretical and experimental bases for the actual treatment of 2,4-DNT, and lays a technical foundation for the bioremediation of organic pollutants.

Optimizing pre-carbonization temperature of sesame residue for hierarchical porous carbon materials in high-performance supercapacitor applications

In this paper, the sesame residue, a common biomass waste, was used as a precursor to synthesize N,O co-doped porous carbon materials via a simple pre-carbonization and KNO3 activation two-step strategy. The apparent morphology and supercapacitor performance of the obtained materials can be regulated by changing the pre-carbonization temperature (0 °C, 300 °C and 600 °C). The consequences demonstrate that a large number of C−C and C−O bonds in sesame residue undergo cleavage and form abundant pore structure at the pre-carbonization temperature of 300 °C. After KNO3 activation, the material has a moderate specific surface area (1073.4 m2 g−1) and affluent heteroatom content (N: 7.52 at%, O: 17.65 at%). As a result, the SS-300 electrode displays exceptional capacitive performance (specific capacitance up to 312.7 F g−1 at 0.5 A g−1) and outstanding cyclic stability (capacitance retention reaching 98.3% at 10 A g−1 after 8000 charge–discharge cycles). Moreover, the symmetric supercapacitor assembled by SS-300 exhibits high energy densities in both 6 M KOH (4.58 Wh kg−1) and 1 M Na2SO4 (15.60 Wh kg−1), highlighting the potential of this material for energy storage applications.